Hyperhomocysteinemia, a condition of elevated plasma homocysteine concentrations resulting from impaired sulfur amino acid metabolism, may be a powerful risk factor for occlusive vascular disease. Hoverer, we know little about the distribution of hyperhomocysteinemia in the general population. Furthermore, inadequate nutritional status might be a strong determinant of hyperhomocysteinemia, but its importance at a population level (as measured by the prevalence of hyperhomocysteinemia associated with inadequate nutrition) has received little study. Finally, levels of homocysteine associated with elevated risk of vascular disease have not been clearly established. To address these issues. CDC has agreed to provide our laboratory with 8,000-9,000 surplus plasma sample from phase 2 of NHANES III. The availability of these plasma samples will provide the unique opportunity to conduct a study in a representative population of the US in which we will: 1) describe the distribution of homocysteine and prevalence of hyperhomocysteinemia with emphasis on race, sex and age; 2) determine the extent to which hyperhomocysteinemia is associated with status of folate and vitamin B12; and 3) describe the relationships between prevalence of hyperhomocysteinemia and prevalence of cardiovascular disease and assess the importance of this risk factor as a cause of vascular disease among US adults. All procedures needed to conduct this study are available in our laboratory and CDC has agreed to provide all additional data needed for successful completion of this project.